Creating triangle commutative diagram with tikz-cd

Update

A better syntax has evolved with time, which has several advantages due to improvements in TikZ and is now recommended.

documentclass{article}
usepackage{tikz-cd}

begin{document}

[
begin{tikzcd}
 & A arrow[dr,"g"] 
B arrow[ur,"f"] arrow[rr,"h"] && C
end{tikzcd}
]
[
begin{tikzcd}[row sep=2.5em]
 & A arrow[dr,"g"] 
B arrow[ur,"f"] arrow[rr,"h"] && C
end{tikzcd}
]
[
begin{tikzcd}[column sep=1.5em]
 & A arrow[dr,"g"] 
B arrow[ur,"f"] arrow[rr,"h"] && C
end{tikzcd}
]
end{document}

Original answer

The basic idea for triangular diagrams is to consider more columns, in this case three; you may want to play with column sep or row sep in order to get better distances, as shown.

documentclass{article}
usepackage{tikz-cd}
begin{document}
[
begin{tikzcd}
 & A arrow{dr}{g} 
B arrow{ur}{f} arrow{rr}{h} && C
end{tikzcd}
]
[
begin{tikzcd}[row sep=2.5em]
 & A arrow{dr}{g} 
B arrow{ur}{f} arrow{rr}{h} && C
end{tikzcd}
]
[
begin{tikzcd}[column sep=1.5em]
 & A arrow{dr}{g} 
B arrow{ur}{f} arrow{rr}{h} && C
end{tikzcd}
]
end{document}

---

If you want to try this with QTikZ, you need a suitable template; create the text file tikz-cd-template.pgs with

documentclass{article}
usepackage{tikz-cd}
begin{document}
<>
end{document}

Choose the template and then paste the part of the above code which is between begin{document} and end{document} in the input window for QTikZ. Here's a picture of the result.

If you have an old version of tikz-cd (which might be the case on Ubuntu or other GNU/Linux boxes) it may be necessary to start the diagram with {}:

[
begin{tikzcd}
{} & A arrow{dr}{g} 
B arrow{ur}{f} arrow{rr}{h} && C
end{tikzcd}
]